Methods and apparatuses for compensating for moisture absorption

ABSTRACT

A technique to characterize moisture in a dielectric layer of a printed circuit board is provided. A method comprises applying a test signal to test circuitry comprising a test capacitor that is formed with the dielectric layer of the printed circuit board; measuring at least one characteristic of a least one of signal transmission and signal reflection from the test circuitry; and determining, from the at least one measured characteristic, at least one parameter value indicative of moisture content in the dielectric layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of U.S. patent application Ser.No. 62/813,901, filed Mar. 5, 2019; the entire contents of theaforementioned patent application are incorporated herein by referenceas if set forth in its entirety.

BACKGROUND

Transmitters are used in communications systems such as base stationsand distributed antenna systems. Transmitters typically employ poweramplifiers to boost the power of a transmitted signal. The poweramplifiers may be built with printed circuit boards (PCBs).

Power amplifiers may be built and tested in one environment and used ina different environment. The two environments may have differenthumidity levels. As a result, the moisture absorption by insulatingmaterial of PCBs may be greater in one environment than the otherenvironment. Variations in moisture in the insulating material affectthe dielectric constant of the insulating material, and loss tangent ofa transmission line made with the insulating material. Changes todielectric constant and loss tangent affects respectively impedancevalues, and loss of transmission lines and capacitance values ofcapacitors formed with the insulating material.

The moisture on surface of the transmission line caused by humidity willaffect the propagation properties especially for higher frequency (skineffect); the moisture can subsequently penetrate the dielectricaffecting capacitance values and affecting transmission line impedance.Moisture in the insulating material of a PCB can be removed by heating acircuit formed with the PCB. Then, the circuit can be hermeticallysealed to preclude subsequent moisture intrusion into the insulatingmaterial. However, this may be cost prohibitive for many applications.Therefore, there is a need for a more cost-effective technique toaddress moisture intrusion in the dielectric material of PCBs.

SUMMARY

A method is presented. The method comprises applying a test signal totest circuitry comprising a test capacitor that is formed with adielectric layer of a printed circuit board; measuring at least onecharacteristic of a least one of signal transmission and signalreflection from the test circuitry; and determining, from the at leastone measured characteristic, at least one parameter value indicative ofmoisture content in the dielectric layer.

DRAWINGS

Understanding that the drawings depict only exemplary embodiments andare not therefore to be considered limiting in scope, the exemplaryembodiments will be described with additional specificity and detailusing the accompanying drawings, in which:

FIG. 1 illustrates one embodiment of a system for compensating formoisture absorption in primary circuitry;

FIG. 2A illustrates a cross section of one embodiment of a capacitor;

FIG. 2B illustrates a cross section of one embodiment of a multi-layercapacitor;

FIG. 3 illustrates a block diagram of one embodiment of moisture sensorcircuitry;

FIG. 4A illustrates a block diagram of one embodiment of a distributedantenna system including at least one moisture compensated poweramplifier;

FIG. 4B illustrates a block diagram of one embodiment of a remoteantenna unit including a moisture compensated power amplifier;

FIG. 5 illustrates a block diagram of one embodiment of a single-noderepeater including a moisture compensated power amplifier; and

FIG. 6 illustrates a flow diagram of one embodiment of a method ofmoisture compensating primary circuitry.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific illustrative embodiments. However, it is tobe understood that other embodiments may be utilized, and thatstructural, mechanical, and electrical changes may be made. Furthermore,the method presented in the drawing figures and the specification is notto be construed as limiting the order in which the individual steps maybe performed. The following detailed description is, therefore, not tobe taken in a limiting sense.

Embodiments of the invention determine a change in capacitance due tomoisture content in a dielectric layer of a PCB. Optionally, theinvention may determine the amount of moisture in the PCB. A user and/orsystem may be alerted to excessive moisture content.

Rather than initially eliminating moisture and preventing subsequentmoisture intrusion—as discussed above, an alternative and morecost-effective technique may be optionally used with the above describedembodiments. Primary circuitry made on and/or with the PCB can includemoisture compensation circuitry (or a portion thereof) to compensate forvariations in moisture content in the dielectric of the PCB. The primarycircuitry may be any circuitry for example any analog, digital, and/ormixed signal circuitry. For pedagogical purposes, a power amplifier willbe subsequently illustrated.

In one embodiment, the moisture compensation circuitry comprises amoisture sensor circuitry and circuitry for adjusting phase and/or gain.The moisture sensor circuitry measures a parameter indicative ofmoisture content in the dielectric material of the PCB, and generates acontrol signal indicating a corresponding change in phase and/or gain.The circuitry for adjusting phase and/or gain is configured to receivethe control signal. Based upon the control signal, the circuitry foradjusting phase and/or gain modifies the phase and/or gain of signalspassing through it.

Only a portion of the moisture compensation circuitry need be formedwith the PCB, e.g. at least one dielectric layer of the PCB and aconductor on or in the PCB. The circuitry for adjusting phase and/orgain may be located elsewhere in a signal chain comprising the primarycircuit. Further, the circuitry for adjusting phase and/or gain may ormay not be co-located with the moisture sensor circuitry.

FIG. 1 illustrates one embodiment of a system for compensating formoisture absorption in primary circuitry (system) 100. The system 100comprises primary circuitry 102 coupled to moisture compensation system104. The moisture compensation system 104 comprises moisture sensorcircuitry 104 a. Optionally, the moisture compensation system 104 (forexample the moisture sensor circuitry 104 a) is configured to send analarm 107, e.g. an alarm signal, to another system or to a user—as isotherwise described herein. Optionally, the moisture compensation system104 includes moisture compensation circuitry 104 b coupled to themoisture sensor circuitry 104 a. The moisture sensor circuitry 104 a isconfigured to generate a control signal 105 that controls the moisturecompensation system 104. FIG. 1 illustrates that the primary circuitry102, the moisture sensor circuitry 104 a, and the moisture compensationcircuitry 104 b are all fabricated using a PCB 106. However, asdiscussed above, the moisture compensation circuitry 104 b need not beformed using the PCB 106, and may be implemented elsewhere in a signalchain (before and/or after the primary circuitry 102). FIG. 1, however,illustrates the moisture compensation circuitry 104 b coupled before theprimary circuitry 102.

The primary circuitry 102 may be a power amplifier used in a transmitsignal chain of a communications system, or any other type of circuitryused in any other type of signal chain. Signal chain means a system ofcomponents coupled together, e.g. serially, to perform any type ofanalog, digital, and/or mixed signal processing.

In one embodiment, the moisture sensor circuitry 104 a is formed byforming a parallel plate capacitor with the PCB 106. FIG. 2A illustratesa cross section of one embodiment of such a capacitor 200A. A firstcapacitor electrode 220 a and a second capacitor electrode 220 b of thecapacitor 222 are formed on the opposing exposed sides of the dielectriclayer 224 of the PCB 206, where one of the sides is where electricalcircuit components 226, e.g. that are part of the moisture sensorcircuitry 104 a and the primary circuitry 102 a are mounted on the PCB206. The first capacitor electrode 220 a and the second capacitorelectrode 220 b typically, but need not, have the same shape and arepositioned as if mirrored around a centerline 228 bisecting thedielectric layer in a plane parallel to the first capacitor electrode220 a and the second capacitor electrode 220 b. The first capacitorelectrode 220 a and the second capacitor electrode 220 b are separatedby a distance D. Each capacitor electrode 220 a, 220 b is made from aconductor.

If the PCB 206 has more than two conductor layers or levels, e.g. is amultilayer PCB, an interdigitated or multi-layer capacitor can beformed. FIG. 2B illustrates a cross section of one embodiment of amulti-layer capacitor 200B. A first set of capacitor electrodes (firstset) is formed by a first capacitor electrode 221 a and a secondcapacitor electrode 221 b are electrical coupled by a first conductivevia 221 c. The first conductive via 221 c in the dielectric layer 224 isformed by filling with a conductor, e.g. a metal or metal alloy, in avia hole in the dielectric layer 224. Optionally, if the PCB 206 has twoor more layers of dielectric, the capacitor is formed across a topdielectric layer exposed to the environment and into which moisturewould first penetrate.

The first capacitor electrode 221 a and the second first capacitorelectrode 221 b typically, but need not, have the same shape and arepositioned as if mirrored around a centerline 228 bisecting thedielectric layer 224 in a plane parallel to the first capacitorelectrode 221 a and second capacitor electrode 221 b. The first set ofcapacitor electrodes may alternatively in include three or morecapacitor electrodes about two or more capacitor electrodes of a secondset of capacitor electrodes (second set). However, for pedagogicalreasons, the illustrated second set of capacitor electrodes has a singlethird capacitor electrode 223 a. The illustrated third capacitorelectrode is coupled by a second conductive via 223 c to a conductiveinterconnect 223 b. The second conductive via 223 c is formed by fillinga via hole in the dielectric layer 224 with a conductor. The firstcapacitor electrode 221 a and the second capacitor electrode 221 b maybe electrically coupled using alternative forms of electrical coupling,e.g. conductive bond ribbons and/or conductive clips formed around theedge of the PCB 206. The various conductors or conductive elementsdescribed herein may be formed with a metal or metal alloy, e.g. gold orcopper.

In one embodiment, the spacings between each of the first capacitorelectrode 221 a and the second capacitor electrode 221 b, and the thirdcapacitor electrode 223 a are equidistance where each spacing has adistance d. The spacing between adjacent electrodes of the first set andthe second set may also be equidistant when the first set and the secondset respectively have more than two and one electrodes. However, inother embodiments, the spacings need not be equidistant. Further, inother embodiments, the capacitor can be formed by only one capacitorelectrode on a surface of the dielectric layer 224, e.g. just the firstcapacitor electrode 221 a, and another capacitor electrode in thedielectric layer 224, e.g. the third capacitor electrode 223 a. In yetanother embodiment, all capacitor electrodes can be within thedielectric layer 224, and not on the surface of the dielectric layer224. In yet a further embodiment, all capacitor electrodes (which areconductors) can be on the same plane on or in the dielectric layer 224;one example would be an interdigitated capacitor where the capacitiveelectrodes of each set of electrodes are formed on the same surface ofthe dielectric layer 224.

FIG. 3 illustrates a block diagram of one embodiment of the moisturesensor circuitry 300. The moisture sensor circuitry 300 may also bereferred to herein as a circuit configured to measure capacitance of acapacitor formed capacitive plates on and/or in the dielectric layer ofthe PCB. In the illustrated embodiment, the capacitor (having acapacitance C) 330, exemplified above in FIGS. 2A and 2B, formed on thePCB 206 is coupled to a signal generator (or square wave signalgenerator) 332 and a processing system 334. The capacitor 330 may alsobe referred to herein as a test capacitor.

The signal generator 332 generates a square wave voltage signal 332 ahaving a peak to peak voltage (V_(g)), and has a characteristicimpedance of Z_(o), e.g. fifty or seventy five ohms, with little or noreactive component. The square wave voltage signal 332 a, having asingle period of 2 t and a peak to peak voltage of V_(g), is illustratedin FIG. 3. The capacitor 330 integrates the square wave voltage signal332 a generating a triangle wave 330 a. The triangle wave 330 a has aperiod of 2 t, and illustrates a voltage (V_(C)) across the capacitor330 and a voltage (V_(r)) across an equivalent series resistance (ESR)of the capacitor 330. V_(c) is amplitude of the slope in the second halfof the period of the square wave signal as illustrated in FIG. 3.

The processing system 334 comprises processing circuitry coupled tomemory circuitry. The memory circuitry may store software and/orfirmware executed by the processing circuitry; else the processingcircuitry may have corresponding instructions encoded in hardware of theprocessing circuitry.

The processing system 334 may also comprise an analog to digitalconverter that converts the analog voltage across the capacitor 330 to adigital signal, e.g. voltage or current, that is coupled to theprocessing circuitry and/or memory circuitry. Alternatively, theprocessing circuitry comprise analog signal processing circuitry.

The processing system 334, e.g. the software and/or firmware, isconfigured to determine the capacitance C of the capacitor 330, where:

$\begin{matrix}{{C = \frac{V_{g}*t}{Z_{o}*V_{C}}},} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$where t is one half of a period of the square wave signal. Optionally,the ESR of the capacitor 330 can be determined, where:

$\begin{matrix}{{ESR} = \frac{V_{R}*Z_{o}}{2*V_{g}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$The processing system 334, e.g. using a digital signal processor as theprocessing circuitry, may determine V_(C), and optionally also V_(r).V_(g), t, and Z_(o) may be stored in the memory circuitry. Thus, usingthe determined and known parameters, the processing circuitry 334 candetermine C and optionally the ESR. For example, the processing system334 e.g. the software and/or firmware, can use curve fitting techniques,such as least means squares techniques, to determine the capacitance C,and optionally the ESR. Further, alternative techniques can be used todetermine the capacitance C, and optionally the ESR, such as for exampletime domain reflectometry or frequency domain reflectometry.

Increased moisture content in the PCB results in decreased or increaseddielectric, depending upon the chemical properties of the moisture, ofthe dielectric material used to make the PCB and also the capacitor 330.Optionally, the processing system 334 may convert the measuredcapacitance to a level of moisture content in the dielectric layer 224.The relationship between the level of moisture content and capacitancemay be determined empirically, and represented by an equation or a lookup table, e.g. stored in the memory circuitry. For example, at roomtemperature, the dielectric constant of the dielectric layer 224 isknown and stored in the processing system 334. The moisture contentmeasured by the moisture sensor is:b*(K−K _(o) −a),  (Equation 3)where K_(o) is a known dielectric constant of the capacitor 330 at withno measurable moisture content, K is the dielectric constantcorresponding to the measured capacitance C, and a and b are constantsthat vary depending upon the type of dielectric material of thedielectric layer 224 and capacitor design. Parameters a and b may beempirically determined. K can be determined, for example using theprocessing system 334 (e.g. firmware and/or software), from thecapacitance C using an equation corresponding to the structure of thecapacitor 330. For a parallel plate capacitor described with respect toFIG. 2A, the dielectric constant

$\begin{matrix}{{K = \frac{C*D}{ɛ_{o}*A}},} & \left( {{Equation}\mspace{14mu} 4} \right)\end{matrix}$where ε_(o) is permittivity in a vacuum, and A is the area of each plate(assuming the plates have the same areas). If the moisture content,capacitance, dielectric, and/or ESR values cross respective thresholdvalues, a system or user may be alerted. As a result of the alert, thesystem or user may alter or disable the operation of the affectedprimary circuit.

Optionally, the processing system 334 may then generate the controlsignal 105 based upon the measured moisture content, capacitance,dielectric constant, and/or ESR. The moisture compensation circuitry 104b is configured to receive such control signal 105. For example, themoisture compensation circuitry 104 b is used to adjust amplitude and/orphase of signals preceding the input of, following the output of, orwithin the primary circuitry 102. Thus, for example, the moisturecompensation circuitry 104 b may precede the input of, follow the outputof, or be part of the primary circuitry 102. For example, when themoisture compensation circuitry 104 b is party of the primary circuitry,the moisture compensation circuitry 104 b may be one or more biascircuits to adjust the bias of one or more active circuits or devices.For pedagogical reasons, the moisture compensation circuitry 104 b isillustrated as separate from and preceding the primary circuitry 102.

The moisture compensation circuitry 104 b may comprise one or more ofswitch(es), amplifier(s), attenuators, phase shifter(s), and/orequalizer(s) which are controlled by the control signal 105. Dependingupon the type(s) of moisture compensation circuitry 104 b used,parameters of the moisture compensation circuitry 104 a are varied inrespond to the control signal 105. The parameters may include amplitude,phase, time delay, and/or any other parameter. For example, the controlsignal 105 may be used to disable operation of the primary circuitry102, e.g. a power amplifier, which may not operate properly or may besusceptible to failure if operated in conditions of excess moisture. Ifone of the parameters, e.g. capacitance, crosses a correspondingthreshold level, then the control signal 105 may be used to increase theattenuation in moisture compensation circuitry 104 b (including anattenuator) at the input of the power amplifier or actuating a switch inseries with a supply voltage of the power amplifier so as to disablepower amplifier operation.

In one embodiment, the primary circuitry 102 is a power amplifier whichcan be implemented in various types of systems, e.g. communicationssystems. For example, the power amplifier can be implemented in varioustypes of repeater systems. Repeater systems can be implemented invarious ways.

For example, a repeater system can be implemented as a distributedantenna system (DAS). FIG. 4A illustrates a block diagram of oneembodiment of a distributed antenna system 400A including at least onemoisture compensated power amplifier.

The DAS 400A comprises one or more master units 402 that arecommunicatively coupled to one or more remote antenna units including amoisture compensated power amplifier (RAUs) 404 via one or morewaveguides 406, e.g. optical fibers or cables. Each RAU 404 can becommunicatively coupled directly to one or more of the master units 402or indirectly via one or more other RAUs 404 and/or via one or moreexpansion (or other intermediary) units 408.

The DAS 400A is coupled to one or more base stations 403 and isconfigured to improve the wireless coverage provided by the one or morebase station 403. The capacity of each base station 403 can be dedicatedto the DAS or can be shared among the DAS and a base station antennasystem that is co-located with the base station and/or one or more otherrepeater systems.

In the embodiment shown in FIG. 4A, the capacity of one or more basestations 403 are dedicated to the DAS 400A. Optionally, the one or morebase stations 403 may be co-located with the DAS 400A. The base stations403 are coupled to the DAS 400A. It is to be understood however thatother embodiments can be implemented in other ways. For example, thecapacity of the one or more base stations 403 can be shared with the DAS400A and a base station antenna system co-located with the one or morebase stations 403 (for example, using a donor antenna). The one or morebase stations 403 can include one or more base stations that are used toprovide commercial cellular wireless service and/or one or more basestations that are used to provide public and/or private safety wirelessservices (for example, wireless communications used by emergencyservices organizations (such as police, fire and emergency medicalservices) to prevent or respond to incidents that harm or endangerpersons or property)).

The one or more base stations 403 can be coupled to the one or moremaster units 402 using a network of attenuators, combiners, splitters,amplifiers, filters, cross-connects, etc., (sometimes referred tocollectively as a “point-of-interface” or “POI”). This network can beincluded in the one or more master units 402 and/or can be separate fromthe one or more master units 402. This is done so that, in the downlink,the desired set of RF channels output by the base stations 403 can beextracted, combined, and routed to the appropriate master unit, and sothat, in the upstream, the desired set of carriers output by the one ormore master units 402 can be extracted, combined, and routed to theappropriate interface of each base station. It is to be understood,however, that this is one example and that other embodiments can beimplemented in other ways.

In general, each master unit comprises downlink DAS circuitry 410 thatis configured to receive one or more downlink signals from one or morebase stations 403. Each base station downlink signal includes one ormore radio frequency channels used for communicating in the downlinkdirection with user equipment 414 over a relevant wireless airinterface. Typically, each base station downlink signal is received asan analog radio frequency signal, though in some embodiments one or moreof the base station signals are received in a digital form (for example,in a digital baseband form complying with the Common Public RadioInterface (“CPRI”) protocol, Open Radio Equipment Interface (“ORP”)protocol, the Open Base Station Standard Initiative (“OBSAI”) protocol,or other protocol). The downlink DAS circuitry 410 in each master unitis also configured to generate one or more downlink transport signalsderived from one or more base station downlink signals and to transmitone or more downlink transport signals to one or more of the RAUs 404.

FIG. 4B illustrates a block diagram of one embodiment of a RAU 404including a moisture compensated power amplifier. Each RAU 404 comprisesa remote unit including a moisture compensated power amplifier (RU) 405coupled to one or more antennas 415. Each RU 405 comprises downlink(D/L) DAS circuitry 412 and uplink (U/L) DAS circuitry 417. The downlinkDAS circuitry 412 includes a transmitter front end (TX FE) 419comprising at least one moisture compensated power amplifier.

The downlink DAS circuitry 412 is configured to receive the downlinktransport signals transmitted to it from one or more master units 402and to use the received downlink transport signals to generate one ormore downlink radio frequency signals that are radiated from the one ormore antennas 415, associated with that RU 405, for reception by userequipment 414. In this way, the DAS 400A increases the coverage area forthe downlink capacity provided by the base stations 403. The downlinkDAS circuitry 412, e.g. the power amplifier(s) in the TX FE 419, of eachRU 405 also power amplify the downlink radio frequency signals.

The uplink DAS circuitry 417 is configured to receive one or more uplinkradio frequency signals transmitted from the user equipment 414. Thesesignals are analog radio frequency signals.

The uplink DAS circuitry 417 in each RU 405 is also configured togenerate one or more uplink transport signals derived from the one ormore remote uplink radio frequency signals and to transmit one or moreuplink transport signals to one or more of the master units 402.

Returning to FIG. 4A, each master unit comprises uplink DAS circuitry416 that is configured to receive the respective uplink transportsignals transmitted to it from one or more RAUs 404 and to use thereceived uplink transport signals to generate one or more base stationuplink radio frequency signals that are provided to the one or more basestations 403 associated with that master unit. Typically, this involves,among other things, combining or summing uplink signals received frommultiple RAUs 404 in order to produce the base station signal providedto each base station. In this way, the DAS 400A increases the coveragearea for the uplink capacity provided by the at least one base stations403.

Each expansion unit 408 comprises downlink DAS circuitry (D/L DAScircuitry) 418 that is configured to receive the downlink transportsignals transmitted to it from the master unit 402 (or another expansionunit 408) and transmits the downlink transport signals to one or moreRAUs 404 or other downstream expansion units 408. Each expansion unit408 also comprises uplink DAS circuitry 420 that is configured toreceive the respective uplink transport signals transmitted to it fromone or more RAUs 404 or other downstream expansion units 408, combine orsum the received uplink transport signals, and transmit the combineduplink transport signals upstream to the master unit 402 or otherexpansion unit 408. In other embodiments, one or more RAUs 404 arecoupled to the one or more master units 402 via one or more other RAUs404 (for example, where the RAUs 404 are coupled together in a daisychain or ring topology).

The downlink DAS circuitry (D/L DAS circuitry) 410, 412, and 418 anduplink DAS circuitry (U/L DAS circuitry) 416, 417, and 420 in eachmaster unit, RAU 404, and expansion unit 408, respectively, can compriseone or more appropriate connectors, attenuators, combiners, splitters,amplifiers, filters, diplexers, duplexers, transmit/receive switches,analog-to-digital converters, digital-to-analog converters,electrical-to-optical converters, optical-to-electrical converters,mixers, field-programmable gate arrays (FPGAs), microprocessors,transceivers, framers, etc., to implement the features described above.Also, the downlink DAS circuitry 410, 412, and 418 and uplink DAScircuitry 416, 417, and 420 may share common circuitry and/orcomponents.

The DAS 400A can use digital transport, analog transport, orcombinations of digital and analog transport for generating andcommunicating the transport signals between the master units 402, theRAU 404, and any expansion units 408. Each master unit 402, RAU 404, andexpansion unit 408 in the DAS 400A also comprises a respectivecontroller (CNTRL) 421. The controller 421 is implemented using one ormore programmable processors that execute software that is configured toimplement the various control functions. The controller 421 (morespecifically, the various control functions implemented by thecontroller 421) (or portions thereof) can be implemented in other ways(for example, in a field programmable gate array (FPGA), applicationspecific integrated circuit (ASIC), etc.). Components of system 100 maybe incorporated in various components of the DAS 400A. For example, theprocessing circuitry 102 and/or portion(s) thereof may be incorporatedin, e.g. the controller 421 of a RAU 404 or in another controller 421incorporated into the distributed antenna system 200A. Further, forexample, the moisture compensation circuitry 104 b may be incorporatedin an equalizer in the master unit 402, expansion unit, and/or one ormore RAUs 404.

Further, a combination of one or more diplexers, duplexers,transmit/receive switches duplexers and/or other combiner systems can beused to couple the downlink DAS circuitry 412 and the uplink DAScircuitry 417 to the one or more antennas 415. The moisture compensatedpower amplifier may be incorporated, e.g. in the controller 421 of a RAU404 or in another controller 421 otherwise incorporated into thedistributed antenna system 400A.

Repeater systems can be implemented in other ways. For example, arepeater system can be implemented as a single-node repeater. FIG. 5illustrates a block diagram of one embodiment of a single-node repeater500 in which the power amplifier with moisture compensation describedherein is implemented.

The single-node repeater 500 comprises downlink repeater circuitry 512and uplink repeater circuitry 520. The downlink repeater circuitry 512is configured to receive, e.g. wirelessly through at least one antenna530 coupled to the single-node repeater 500, one or more downlinksignals from one or more base stations 503 coupled to one or moreantennas 504. These signals are also referred to here as “base stationdownlink signals.” Each base station downlink signal includes one ormore radio frequency channels used for communicating in the downlinkdirection with user equipment (UE) 514 over a relevant wireless airinterface. Typically, each base station downlink signal is received asan analog radio frequency signal.

The downlink repeater circuitry 512 in the single-node repeater 500 isalso configured to generate one or more downlink radio frequency signalsthat are radiated from one or more antennas 515 associated with thesingle-node repeater 500 for reception by user equipment 514. Thesedownlink radio frequency signals are analog radio frequency signals andare also referred to here as “repeated downlink radio frequencysignals.” Each repeated downlink radio frequency signal includes one ormore of the downlink radio frequency channels used for communicatingwith user equipment 514 over the wireless air interface. In thisexemplary embodiment, the single-node repeater 500 is an active repeatersystem in which the downlink repeater circuitry 512 comprises one ormore amplifiers (or other gain elements) that are used to control andadjust the gain of the repeated downlink radio frequency signalsradiated from the one or more antennas 515. Each of the downlinkrepeater circuitry 512 and the uplink repeater circuitry 520 include atleast one transmitter front end including a moisture compensated poweramplifier (TX FE) 519 which, for example, power amplifies respectivelythe repeated downlink and uplink radio frequency signals. Such moisturecompensated power amplifiers may be implemented as described above.

The uplink repeater circuitry 520 is configured to wirelessly receivethrough the one or more antennas 515 one or more uplink radio frequencysignals transmitted from the user equipment 514. These signals areanalog radio frequency signals and are also referred to here as “UEuplink radio frequency signals.” Each UE uplink radio frequency signalincludes one or more radio frequency channels used for communicating inthe uplink direction with user equipment 514 over the relevant wirelessair interface.

The uplink repeater circuitry 520 in the single-node repeater 500 isalso configured to generate one or more uplink radio frequency signalsthat are wirelessly communicated through the at least one antenna 530 tothe one or more base stations 503. These signals are also referred tohere as “repeated uplink signals.” Each repeated uplink signal includesone or more of the uplink radio frequency channels used forcommunicating with user equipment 514 over the wireless air interface.In this exemplary embodiment, the single-node repeater 500 is an activerepeater system in which the uplink repeater circuitry 520 comprises oneor more amplifiers (or other gain elements) that are used to control andadjust the gain of the repeated uplink radio frequency signals providedto the one or more base stations 503. Typically, each repeated uplinksignal is provided to the one or more base stations 503 as an analogradio frequency signal.

The downlink repeater circuitry 512 and uplink repeater circuitry 520can comprise one or more appropriate connectors, attenuators, combiners,splitters, amplifiers, filters, diplexers, duplexers, transmit/receiveswitches, analog-to-digital converters, digital-to-analog converters,electrical-to-optical converters, optical-to-electrical converters,mixers, field-programmable gate arrays (FPGAs), microprocessors,transceivers, framers, etc., to implement the features described above.Also, the downlink repeater circuitry 512 and uplink repeater circuitry520 may share common circuitry and/or components.

Further, a combination of two or more diplexers, duplexers,transmit/receive switches duplexers and/or other combiner systems can beused to couple the downlink DAS circuitry 512 and the uplink DAScircuitry 520 to one or more antennas 515. The single-node repeatersystem 500 also comprises a controller (CNTRL) 521. The controller 521is implemented using one or more programmable processors that executesoftware that is configured to implement the various control functions.The controller 521 (more specifically, the various control functionsimplemented by the controller 521) (or portions thereof) can beimplemented in other ways (for example, in a field programmable gatearray (FPGA), application specific integrated circuit (ASIC), etc.). Thecomponents of the moisture compensated power amplifier system may beincorporated in various components of the single-node repeater system500 like as described above for the DAS 400.

FIG. 6 illustrates a flow diagram of one embodiment of a method ofmoisture compensating primary circuitry 600. To the extent that theembodiment of method 600 shown in FIG. 6 is described herein as beingimplemented in the systems described with respect to FIGS. 1-5, it is tobe understood that other embodiments can be implemented in other ways.The blocks of the flow diagrams have been arranged in a generallysequential manner for ease of explanation; however, it is to beunderstood that this arrangement is merely exemplary, and it should berecognized that the processing associated with the methods (and theblocks shown in the Figures) can occur in a different order (forexample, where at least some of the processing associated with theblocks is performed in parallel and/or in an event-driven manner).

In block 660, apply a test signal, e.g. a square wave voltage signal,sinusoidal voltage signal, or any other type of signal, to a testcircuitry comprising a test capacitor that is formed with a dielectriclayer of a PCB. The test signal, e.g. the sinusoidal voltage signal, maybe fixed or varied in frequency. In block 662, measure at least one ofsignal transmission and signal reflection from the test circuitry. Inblock 664, determine at least one parameter value indicative of moisturecontent of the dielectric layer; optionally the at least one parameterincludes at least one of test capacitor capacitance, dielectric constantof the test capacitor, moisture content of the dielectric layer, and theESR of the test capacitor. Optionally, determine at least one othercircuit element parameter value from the measured signal; such othercircuit element parameter values may include a resistance of a resistorin series or shunt with test capacitor.

Optionally, in block 668, determine whether at least one or moreparameter values indicative of moisture content cross correspondingparameter threshold value(s). If not, return to block 660. If yes,proceed to block 670.

For example, optionally, determine if the capacitance value crosses acapacitance threshold value. Crossing a threshold value means one ofgreater than or less than the threshold value. Whether crossing thethreshold value means greater than or less than depends upon thecorresponding parameter. For example, crossing a moisture contentthreshold value means that the determined moisture content is greaterthan the determined moisture content.

In block 670, if one or more threshold values are crossed, send an alarm(or alarm signal) to another system or user. Optionally, the alarmidentifies the primary circuitry having excessive moisture content. Thesystem or user may then elect to replace and/or disable the primarycircuitry affected by excess moisture content.

Optionally, in block 672, generate a control signal with informationbased upon at least one of at least one of capacitance value, ESR value,moisture content value, and dielectric constant value. The informationmay be data modulated on a carrier wave, parameters (such as frequency)of the carrier wave, etc. Optionally, in block 674, modify signalsgenerated by the primary circuitry based upon information in the controlsignal. Signals generated by the primary circuitry may be modified, forexample, by affecting:

(a) operation of the primary circuitry such as by disabling the primarycircuitry or by controlling a circuit element of the primary circuitry;and

(b) operation of a component external to the primary circuitry, e.g.preceding or following the primary circuitry in the signal chain.Examples of such components are provided elsewhere herein.

The processing circuitry described herein may include one or moremicroprocessors, microcontrollers, digital signal processing (DSP)elements, application-specific integrated circuits (ASICs), complexprogrammable logic devices, and/or field programmable gate arrays(FPGAs). In this exemplary embodiment, processing circuitry includes orfunctions with software programs, firmware, or other computer readableinstructions for carrying out various process tasks, calculations, andcontrol functions, used in the methods described herein. Theseinstructions are typically tangibly embodied on any storage media (orcomputer readable medium) used for storage of computer readableinstructions or data structures. Alternatively, all or part of theprocessing circuitry may be implemented with analog processingcircuitry, e.g. implemented with operational amplifier(s).

The memory circuitry described herein can be implemented with anyavailable storage media (or computer readable media) that can beaccessed by a general purpose or special purpose computer or processor,or any programmable logic device. Suitable computer readable medium mayinclude storage or memory media such as semiconductor, magnetic, and/oroptical media. For example, computer readable media may includeconventional hard disks, Compact Disk-Read Only Memory (CD-ROM), DVDs,volatile or non-volatile media such as Random Access Memory (RAM)(including, but not limited to, Dynamic Random Access Memory (DRAM)),Read Only Memory (ROM), Electrically Erasable Programmable ROM (EEPROM),and/or flash memory. Combinations of the above are also included withinthe scope of computer readable media.

EXEMPLARY EMBODIMENTS

Example 1 includes a method, comprising: applying a test signal to testcircuitry comprising a test capacitor that is formed with a dielectriclayer of a printed circuit board (PCB); measuring at least onecharacteristic of a least one of signal transmission and signalreflection from the test circuitry; and determining, from the at leastone measured characteristic, at least one parameter value indicative ofmoisture content in the dielectric layer.

Example 2 includes the method of Example 1, wherein the test signalcomprises one of a square wave voltage signal or a sinusoidal voltagesignal.

Example 3 includes the method of Example 2, wherein a frequency of thesinusoidal voltage signal is varied.

Example 4 includes the method of any of Examples 1-3, wherein the atleast one parameter value indicative of the moisture content of thedielectric layer comprises at least one of capacitance of the testcapacitor, an effective series resistance of the test capacitor, adielectric constant of the test capacitor, and a moisture content of thedielectric layer of the PCB.

Example 5 includes the method of any of Examples 1-4, further comprisingdetermining whether one or more of the parameter values crossedcorresponding parameter threshold value(s).

Example 6 includes the method of Example 5, further comprising if atleast one threshold value is crossed, sending an alarm to another systemor user.

Example 7 includes the method of any of Examples 1-5, furthercomprising: generating a control signal with information based upon atleast one of a capacitance value, an ESR value, a moisture contentvalue, and a dielectric constant value; and modifying signals generatedby the primary circuitry based upon the information.

Example 8 includes the method of Example 7, wherein modifying signalsgenerated by the primary circuit comprises modifying at least one ofamplitude and phase of at least one of an input signal to and an outputsignal from the primary circuitry.

Example 9 includes a system, comprising: a printed circuit board (PCB)comprising at least one dielectric layer; primary circuitry formed atleast one of on or with the PCB; and moisture sensor circuitrycomprising a test capacitor formed with the at least one dielectriclayer and at least one conductor on or in the dielectric layer, andconfigured to measure at least one characteristic of a least one ofsignal transmission and signal reflection from the test circuitry.

Example 10 includes the system of Example 9, wherein the at least oneparameter value indicative of the moisture content of the dielectriclayer comprises at least one of capacitance of the test capacitor, aneffective series resistance of the test capacitor, a dielectric constantof the test capacitor, and a moisture content of the dielectric layer ofthe PCB.

Example 11 includes the system of any of Examples 9-10, wherein themoisture sensor circuitry is configured to be coupled to moisturecompensation circuitry which is at least one of coupled to and a part ofthe primary circuitry.

Example 12 includes the system of any of Examples 9-11, wherein themoisture sensor circuitry is further configured to determine, from theat least one measured characteristic, at least one parameter valueindicative of moisture content in the dielectric layer.

Example 13 includes the system of Example 12, wherein the moisturesensor circuitry is further configured to send an alarm to anothersystem or user if one or more of the parameter values crossedcorresponding parameter threshold value(s).

Example 14 includes the system of Examples 9-13, further comprising amoisture compensation circuitry that is at least one of coupled to andpart of the primary circuitry; wherein the moisture sensor circuitry isfurther configured to generate a control signal with information basedupon at least one of a capacitance value, an ESR value, a moisturecontent value, and dielectric constant value; and wherein signalsgenerated by the primary circuitry are modified based upon theinformation.

Example 15 includes the system of Example 14, wherein the moisturecompensation circuitry is an equalizer in a signal chain including theprimary circuitry.

Example 16 includes the system of any of Examples 9-15, wherein the testcapacitor is a parallel plate capacitor having electrodes on opposingsides of a dielectric layer.

Example 17 includes the system of any of Example 9-16, wherein themoisture sensor circuitry further comprises: a signal generator coupledto both terminals of the test capacitor and configured to generate asquare wave having a period T; a processing system, comprisingprocessing circuitry coupled to memory circuitry, coupled to bothterminals of the test capacitor; and wherein the test capacitorintegrates the square wave; and wherein determining at least oneparameter indicative of moisture content is determined, by theprocessing system, from the integrated square wave.

Example 18 includes the system of any of Examples 9-17, wherein theprimary circuitry is a power amplifier.

Example 19 includes the system of any of Examples 9-18, wherein systemcomprises one of a remote antenna unit of a distributed antenna systemand a single-node repeater.

Example 20 includes a program product comprising a non-transitoryprocessor readable medium on which program instructions are embodied,wherein the program instructions are configured, when executed by atleast one programmable processor, to cause the at least one programmableprocessor to: cause a signal generator to apply a test signal to testcircuitry comprising a test capacitor that is formed with a dielectriclayer of a printed circuit board (PCB); measure at least onecharacteristic of a least one of signal transmission and signalreflection from the test circuitry; and determine, from the at least onemeasured characteristic, at least one parameter value indicative ofmoisture content in the dielectric layer.

Example 21 includes the program product of Example 20, wherein the atleast one parameter value indicative of the moisture content of thedielectric layer comprises at least one of capacitance of the testcapacitor, an effective series resistance of the test capacitor, adielectric constant of the test capacitor, and a moisture content of thedielectric layer of the PCB.

Example 22 includes the program product of any of Examples 20-21,wherein the program instructions are configured, when executed by atleast one programmable processor, to further cause the at least oneprogrammable processor to determine, from the at least one measuredcharacteristic, at least one parameter value indicative of moisturecontent in the dielectric layer.

Example 23 includes the program product of any of Examples 20-22,wherein the program instructions are configured, when executed by atleast one programmable processor, to further cause the at least oneprogrammable processor to send an alarm to another system or user if atleast one threshold value is crossed.

Example 24 includes the program product of any of Examples 20-23,wherein the program instructions are configured, when executed by atleast one programmable processor, to further cause the at least oneprogrammable processor to: generate a control signal with informationbased upon at least one of a capacitance value, an ESR value, a moisturecontent value, and a dielectric constant value; and modify signalsgenerated by the primary circuitry based upon the information.

The terms “about” or “substantially” indicate that the value orparameter specified may be somewhat altered, as long as the alterationdoes not result in nonconformance of the process or structure to theillustrated embodiment. Finally, “exemplary” indicates the descriptionis used as an example, rather than implying that it is an ideal.

Terms of relative position as used in this application are defined basedon a plane parallel to the conventional plane or working surface of alayer or substrate, regardless of orientation. The term “horizontal” or“lateral” as used in this application are defined as a plane parallel tothe conventional plane or working surface of a layer or substrate,regardless of orientation. The term “vertical” refers to a directionperpendicular to the horizontal. Terms such as “on,” “side” (as in“sidewall”), “higher,” “lower,” “over,” “top,” and “under” are definedwith respect to the conventional plane or working surface being on thetop surface of a layer or substrate, regardless of orientation.

A number of embodiments of the invention defined by the following claimshave been described. Nevertheless, it will be understood that variousmodifications to the described embodiments may be made without departingfrom the spirit and scope of the claimed invention. Accordingly, otherembodiments are within the scope of the following claims. Therefore, itis manifestly intended that this invention be limited only by the claimsand the equivalents thereof.

The invention claimed is:
 1. A method, comprising: applying a testsignal to test circuitry comprising a test capacitor that is formed witha dielectric layer of a printed circuit board (PCB); measuring a voltageacross the test capacitor that is formed with the dielectric layer ofthe PCB; and determining, from the measured voltage, at least one of (a)a capacitance and an equivalent series resistance (ESR) of the testcapacitor formed with the dielectric layer of the PCB, and (b) amoisture content of the dielectric layer of the PCB.
 2. The method ofclaim 1, wherein the test signal comprises one of a square wave voltagesignal or a sinusoidal voltage signal.
 3. The method of claim 2, whereina frequency of the sinusoidal voltage signal is varied.
 4. The method ofclaim 1, further comprising determining whether one or more ofdetermined parameter values crosses corresponding parameter thresholdvalue(s).
 5. The method of claim 4, further comprising determining thatparameter threshold value(s) have been crossed, then sending an alarm toanother system or a user.
 6. The method of claim 1, further comprising:generating a control signal with information based upon at least one of(a) the determined capacitance, (b) the determined ESR, and (c) thedetermined moisture content; and modifying signals generated by aprimary circuitry based upon the information.
 7. The method of claim 6,wherein modifying signals generated by the primary circuitry comprisesmodifying at least one of amplitude, phase, and time delay of at leastone of fa) an input signal to the primary circuitry and an output signalfrom the primary circuitry.
 8. A system, comprising: a printed circuitboard (PCB) comprising at dielectric layer; primary circuitry formed atleast one of on or with the PCB; and moisture sensor circuitrycomprising a test capacitor formed with the dielectric layer of the PCBand at least one conductor on or in the dielectric layer, and configuredto apply a test signal to the test capacitor formed with the dielectriclayer of the PCB, measure a voltage across the test capacitor formedwith the dielectric layer of the PCB and determine, from the measuredvoltage, at least one of (a) a capacitance and an equivalent seriesresistance (ESR) of the test capacitor formed with the dielectric layerof the PCB, and (b) a moisture content of the dielectric layer of thePCB.
 9. The system of claim 8, wherein the moisture sensor circuitry isconfigured to be coupled to moisture compensation circuitry which is atleast one of (a) coupled to a part of the primary circuitry and (b) thepart of the primary circuitry.
 10. The system of claim 8, wherein themoisture sensor circuitry is further configured to send an alarm toanother system or an user if at least one of the determined capacitance,the determined ESR, and the determined moisture content crossescorresponding parameter threshold value(s).
 11. The system of claim 8,further comprising moisture compensation circuitry that is at least oneof (a) coupled to the primary circuitry and (b) part of the primarycircuitry; and wherein the moisture sensor circuitry is furtherconfigured to generate a control signal with information based upon atleast one of La) the determined capacitance, and the determined ESR, and(b) the determined moisture content; wherein signals generated by theprimary circuitry are modified based upon the information.
 12. Thesystem of claim 8, wherein the test capacitor is a parallel platecapacitor having electrodes on opposing sides of the dielectric layer.13. The system of claim 8, wherein the moisture sensor circuitry furthercomprises: a signal generator coupled to both terminals of the testcapacitor and configured to generate the test signal that is a squarewave voltage signal which has a period T; a processing circuitry,coupled to both terminals of the test capacitor; and wherein the testcapacitor is configured to integrate the square wave voltage signal;wherein the processing circuitry is configured to determine thecapacitance and the equivalent series resistance of the test capacitorwhen the square wave voltage signal is applied to the test capacitor isdetermined from an integrated square wave voltage signal.
 14. The systemof claim 8, wherein the primary circuitry is a power amplifier.
 15. Thesystem of claim 8, wherein the system comprises one of (a) a remoteantenna unit of a distributed antenna system and (b) a single-noderepeater.
 16. A program product comprising a non-transitory processorreadable medium on which program instructions are embodied, wherein theprogram instructions are configured, when executed by at least oneprogrammable processor, to cause the at least one programmable processorto: cause a signal generator to apply a test signal to test circuitrycomprising a test capacitor that is formed with a dielectric layer of aprinted circuit board (PCB); obtain a measurement of a measured voltageacross the test capacitor that is formed with the dielectric layer ofthe PCB; and determine, from the measured voltage, at least one of, (a)a capacitance and an equivalent series resistance (ESR) of the testcapacitor formed with the dielectric layer of the PCB, and (b) amoisture content of the dielectric layer of the PCB.
 17. The programproduct of claim 16, wherein the program instructions are configured,when executed by the at least one programmable processor, to furthercause the at least one programmable processor to determine that one ormore parameter threshold value(s) crosses corresponding parameterthreshold value(s), and send an alarm to another system or an user. 18.The program product of claim 16, wherein the program instructions areconfigured, when executed by the at least one programmable processor, tofurther cause the at least one programmable processor to: causegeneration of a control signal with information based upon at least oneof (a) the determined capacitance, the determined ESR, and (b) thedetermined moisture content; and cause modification of signals generatedby a primary circuitry based upon the information.